A wide variety of guidewires are used for various medical purposes in the treatment of the human body. Typically guidewires are used to guide a catheter to a site within a patient's blood vessel to perform the procedure for which the catheter is adapted. For example, guidewires, particularly small diameter steerable guidewires, perform the important function in percutaneous transluminal coronary angioplasty of guiding a balloon catheter such that the balloon can be placed at the site of the stenosis (obstruction) to be treated. The balloon is then inflated to dilate the stenosis and subsequently increase the blood flow through the artery.
Typical angioplasty steerable guidewires include a torsionally rigid, longitudinally flexible shaft and a flexible distal end that includes a coil, all or part of which may be radiopaque, so that a physician can monitor fluoroscopically the position and advancement of the guidewire.
During procedures, such as coronary angioplasty, it is often the practice to inject a radiopaque contrast liquid into the artery so that the shape and path of the artery, particularly in the region of the stenosis, may be visualized fluoroscopically. The radiopacity of some guidewire coils may be so dense as to visually obstruct the stenosed part of the artery when the contrast liquid is injected. As a result of the visual obstruction, the ability of the physician to visualize and assess the nature of the stenosis is impaired.
U.S. Pat. No. 5,144,959 (Gambale) describes a guidewire which does not visually obstruct the desired part of the artery when contrast liquid is injected. The distal region of the Gambale guidewire includes a coil having a highly radiopaque distal portion, a moderately radiopaque proximal portion and a non-radiopaque intermediate portion. The guidewire may be advanced so that its distal portion advances through and beyond the stenosis while the non-radiopaque portion is disposed at the region of the stenosis to prevent visual obstruction. The moderately radiopaque proximal portion provides an indication of the position and configuration of the more proximally located portions of the guidewire. Thorough assessment of the stenosis, however, is difficult without the provision of a visual reference length.
The provision of a visible reference length would enable the physician to make in vivo measurements of the lesion to determine its length and shape and dimensions of the artery adjacent to the lesion. The assessment facilitates the selection of an appropriately sized balloon catheter and, additionally, in the event that a stent is needed to prevent the artery from collapsing in the area of the lesion, aids in the selection of an appropriately sized stent. It is, therefore, desirable for the distal region of non-obstructing guidewires to include a highly radiopaque distal section and more proximal uniformly spaced radiopaque markers, which provide such a reference length.
It is among the general objects of the invention to provide guidewires having the foregoing desirable characteristics.